This invention relates to a fluid spring for protecting a structural element from the potential effects of a cyclic event.
In U.S. Pat. Nos. 5,526,609 and 5,765,313 to Lee et al. there is disclosed both method and apparatus for a real time structural parameter modification (RSPM) in which a mechanical spring is engaged and disengaged with a structural element by means of a hydraulic switch. When engaged, the spring acts to stiffen the structural element and store energy when the structure experiences a potentially harmful cyclic event. The stored energy is released from the system by disengaging the spring from the structural element. After the stored energy is released, the structural element is once again engaged by the spring and the cycle is repeated.
In the RSPM system the mechanical spring and the hydraulic switch are separate elements. The size of the apparatus, and in particular the spring, are relatively large and thus occupy a good deal of space. The reaction time needed to engage and disengage the spring is also relatively long diminishing the ability of the system to react to high shock loads. Any delay in responding to high shock loads can result in unacceptable G-loads.